Stolen car debt

Did you not have insurance?

If you didnt have insurance, or enough of it, you would still be responsible for whatever remaining balance.

Unfortunately, yes. The fact that the collateral doesn't exist or isn't in your possession anymore doesn't relieve you of your obligation to repay the underlying debt. It just means there's no car for them to repossess.

Put yourself in their shoes and think about it logically. Suppose that you had a friend that wanted to buy a car but didn't have enough cash to buy it outright, and so you wrote a check to the dealer for that car, and your friend promised to pay you back. Now if the car was stolen from your friend and he still owed you $5K, would you say "Well I guess you don't have the car anymore so you don't have to pay me back anymore."

Chances are that, being 5 years old, it's a dead file to the lender and they are not actively pursuing it. If they were going to sue over it, they'd probably have done so by now. But it can and will show up on your credit report until paid. Or else is will drop off your credit report 7.5 years after the loan defaulted.